WASHINGTON - Osama bin Laden's terrorist network has been pursuing a sophisticated biological weapons research program and is seeking chemical weapons, the Pentagon has told Congress.

Other terrorist groups and dozens of countries also are pursuing chemical and biological weapons, which could be used in a regional conflict or terrorist attack, the military said in a report.

"The relative ease of producing some chemical or biological agents has increased concern that their use may become more attractive to terrorist groups intent on causing panic or inflicting large numbers of casualties," the Pentagon report said.

The report also said companies in Russia and China are the key suppliers of the know-how and equipment for countries like Iran trying to develop their own biological and chemical weapons. It said Iran and Syria have chemical weapons and may be trying to make biological weapons, and Libya is trying to make both.

Al-Qaida's interest in chemical, biological and nuclear weapons has long been known. Bin Laden has said Muslims have a religious duty to make and use weapons of mass destruction against Americans and Jews.

American forces in Afghanistan discovered documents and equipment showing often crude attempts by the terrorist network to develop chemical weapons and strong interest in biological weapons. The Pentagon report, sent to Congress in April and disclosed in a news release late Thursday, is the first government document to say al-Qaida had a sophisticated biological weapons development effort.

The Pentagon report does not offer any more details on that germ weapons effort.

An FBI bulletin last month said the capture of al-Qaida operations chief Khalid Shaikh Mohammed provided fresh evidence of the terror network's experiments with chemical and biological weapons.

U.S. officials say al-Qaida is linked to several men arrested in London in conjunction with the discovery of traces of the biological toxin ricin. Officials say the men were part of Ansar al-Islam, an al-Qaida-linked group that operated out of northern Iraq before U.S. and Kurdish forces destroyed their headquarters during the war in Iraq.

While ricin is extremely deadly and has no antidote, it can be produced easily from the beans of the castor plant.

"The threat of terrorists obtaining and employing biological or chemical materials has increased" in the wake of the Sept. 11, 2001, terrorist attacks, the Pentagon report said.

But the report also noted that creating ways to deliver such weapons to kill large numbers of people requires sophisticated technology that's beyond the reach of most terrorist groups and many countries.

On the other hand, crude weapons could be made by "almost any nation or group." While unsophisticated weapons might kill only a few, "they could have significant operational repercussions due to the psychological impact created by fears" of chemicals or germs, the report said.

The report says "entities in Russia and China" are the main suppliers of equipment and technology related to biological and chemical weapons. Russia, in particular, has been a source of equipment and expertise for Iran's chemical and biological weapons programs, it said.

Iran has denied having chemical, biological or nuclear weapons programs. The Pentagon report says Iran may have some biological weapons stocks and has stockpiled chemical weapons.

Syria also denies it has chemical or biological weapons. The Pentagon report says Syria has stockpiles of the nerve agent Sarin and is seeking to make the more sophisticated nerve agent VX. The report also says Syria "is believed to be pursuing the development of biological weapons" but is not believed to have progressed beyond the research phase.

The report says Libya also is trying to make biological and chemical weapons but has not had much success. It says Libya resumed contacts with outside suppliers for possible chemical weapons material after the United Nations lifted sanctions against it in 1999.